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      <title>说说你对分层编译的理解 - 交互式测验</title>
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    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>说说你对分层编译的理解 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
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      <script>
        const quizData = [
  {
    "question": "JVM引入分层编译（Tiered Compilation）机制的主要目的是什么？",
    "options": [
      "完全取代解释器，让所有代码从一开始就以最高效的机器码运行。",
      "在应用的启动速度和长期运行的峰值性能之间取得平衡。",
      "仅仅为了加快应用的启动速度，而不关心后期的性能。",
      "降低编译过程中的内存消耗，但会牺牲执行效率。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "分层编译的核心目标是在编译开销和运行时性能之间找到最佳平衡点。它通过在应用启动初期使用解释执行（Tier 0）和轻量级的C1编译来保证快速启动，然后对频繁执行的“热点代码”逐步应用C2编译器的深度优化，以实现长期的峰值性能。",
    "source": "文档中「分层编译概述」部分",
    "hint": "文档提到，此机制旨在“平衡编译时间与运行时性能”。"
  },
  {
    "question": "在分层编译中，C1编译器和C2编译器的核心职责区别是什么？",
    "options": [
      "C1编译器负责快速、轻量级的编译，旨在迅速提升性能；而C2编译器则进行深度、复杂的优化，以达到最高的执行效率。",
      "C1编译器只用于客户端桌面应用，C2编译器只用于服务器端应用。",
      "C1编译器将Java源代码编译为字节码，C2编译器将字节码编译为机器码。",
      "C1编译器处理Tier 4的编译，而C2编译器处理Tier 1到Tier 3。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "C1（Client Compiler）是轻量级编译器，它的目标是快速生成优化程度较低的机器码，以缩短编译时间，适用于启动阶段或执行频率不高的代码。C2（Server Compiler）是重量级编译器，它会进行深度和复杂的优化，虽然编译耗时较长，但能生成性能极高的机器码，适用于“长期热点”代码。",
    "source": "文档中「分层编译概述」->「4. C1与C2编译器」部分",
    "hint": "一个的特点是“较轻量，着眼于快速生成”，另一个是“功能更强大，能够进行深度优化”。"
  },
  {
    "question": "根据文档，分层编译的最高级别Tier 4是由哪个编译器负责，并且它采用了哪些优化策略？",
    "options": [
      "由C1编译器负责，它只进行简单的字节码到机器码的转换。",
      "由解释器直接优化，通过记录运行时数据来改进执行。",
      "由C2编译器负责，但它只进行分支预测和死代码消除等轻量优化。",
      "由C2编译器负责，它会使用逃逸分析、方法内联、循环展开等深度优化技术。"
    ],
    "correctAnswerIndex": 3,
    "explanation": "Tier 4是分层编译的最高级别，专门处理被识别为“长期热点”的代码。这个级别由C2编译器（Server Compiler）执行，它会利用大量的运行时分析数据进行深度优化，包括逃逸分析、方法内联、循环展开、去虚拟化等复杂技术，以实现最高的执行性能。",
    "source": "文档中「分层编译的级别」->「5. Tier 4 - C2编译器（深度优化）」部分",
    "hint": "最高级别的编译会使用最强大的编译器和最复杂的优化手段。"
  },
  {
    "question": "JVM的层级切换机制是如何识别出需要升级编译级别的“热点代码”的？",
    "options": [
      "通过在代码编译前进行静态分析，预测哪些代码会成为热点。",
      "通过方法执行计数器和循环计数器来监控代码的执行频率，当执行次数达到预设阈值时触发编译升级。",
      "由程序员在代码中手动添加注解来标记热点方法。",
      "在每个固定时间间隔（如1秒）随机选择一些方法进行编译升级。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "JVM的层级切换依赖于热点探测机制。该机制通过为每个方法和循环维护计数器来工作。当一个方法的调用次数或一个循环的执行次数超过了设定的阈值，JVM就会认为它是“热点”，并将其提交给更高层级的JIT编译器进行优化。",
    "source": "文档中「层级切换机制」->「2. 热点探测与执行计数」部分",
    "hint": "文档中提到了两种关键的“计数器”用于触发层级切换。"
  },
  {
    "question": "与分层编译（采用JIT）相比，AOT（Ahead-Of-Time）编译最显著的优势是什么？",
    "options": [
      "启动速度快，因为代码在应用程序运行前就已经被编译成本地机器码。",
      "能够根据程序运行时的动态行为进行更深度的优化。",
      "编译后的代码包体积更小，占用更少的磁盘空间。",
      "拥有更好的跨平台可移植性，一份编译产物可以在所有操作系统上运行。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "AOT编译在程序运行前就将代码编译为目标平台的机器码。因此，在应用启动时，无需再花费时间和CPU资源进行解释执行或JIT编译，从而显著加快了启动速度。而分层编译（JIT）的优势在于能够利用运行时信息进行动态深度优化。",
    "source": "文档中「与AOT编译的对比」->「启动速度与响应时间」部分",
    "hint": "“Ahead-Of-Time”这个名字本身就暗示了它的编译发生在哪个阶段，这直接影响了程序的启动过程。"
  },
  {
    "question": "在什么情况下，JVM可能会对一个已经被深度优化的方法进行“动态降级”？",
    "options": [
      "当JVM检测到有新的、更优化的编译算法可用时。",
      "当方法被成功执行一百万次后，JVM会将其降级以释放资源。",
      "如果该方法的执行频率在一段时间后大幅下降，JVM会将其降级以减少维护成本。",
      "动态降级是不可逆的，一旦降级，方法将永远保持在较低级别。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "JVM的层级切换是动态和双向的。如果一个之前被判定为热点并由C2编译器优化到Tier 4的方法，在后续的运行过程中执行频率显著降低，JVM可能会将其降级到较低的编译层级。这样做是为了避免对不再频繁执行的代码保持过度优化，从而释放资源并降低维护成本。",
    "source": "文档中「层级切换机制」->「4. 层级切换的反馈机制」部分",
    "hint": "层级切换机制是双向的，不仅有升级，也有适应变化的“降级”过程。"
  },
  {
    "question": "开发者希望为一个对启动速度要求极高、但生命周期很短的工具程序进行JVM调优，以下哪个调优策略最不适合？",
    "options": [
      "降低 `-XX:CompileThreshold` 的值，让代码尽快进入C2深度优化。",
      "使用 `-XX:TieredStopAtLevel=1` 来限制编译层级，避免C2编译开销。",
      "增大 `-XX:CompileThreshold` 的值，减少编译的触发。",
      "采用AOT编译技术替代JIT。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "对于生命周期短且要求快速启动的应用，其代码可能在程序结束前都无法从高昂的C2编译成本中获益。降低编译阈值（CompileThreshold）会让JVM更早、更频繁地尝试进行编译，甚至触发重量级的C2编译，这会消耗宝贵的启动时间和CPU资源，与“快速启动”的目标背道而驰。更合适的策略是限制或延迟高级别编译。",
    "source": "文档中「分层编译的调优」->「（2）调整编译阈值」和「应用场景与最佳实践」部分",
    "hint": "思考一下，对于一个“跑得快但跑不远”的程序，花费大量时间进行“热身”（深度编译）是否划算？"
  }
];
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        }
        
        function showHint() {
            const currentQuestion = quizData[currentQuestionIndex];
            if (currentQuestion.hint) {
                hintContainerEl.textContent = currentQuestion.hint;
                hintContainerEl.style.display = 'block';
            } else {
                hintContainerEl.style.display = 'none';
            }
        }

        function showFinalScore() {
            document.querySelector('.quiz-body').style.display = 'none';
            document.getElementById('quiz-footer').style.display = 'none';

            const correctCount = score;
            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  